Demand indicator



Nov. 12, 1935.

H. DALLMANN DEMAND INDICATOR Filed March 23, 1935 Herbert 'Daflmann 135 N 6. His Attorne g.

Patented Nev. 12 1935 UN E S ATES P us-renter nnm'nvp mmcs'ron Herbert mum Berlin-Karlshorst, Germany," assignor to General Electric Company, a corpo-' ration of New York Application March 23, 1935, Serial No. 12,611

In Germany June 27, 1934 tion receive relatively more weight than sus- .tained peaks, and receive progressively less 15 weight the longer they, are sustained. I

It is a further object of my invention to pros videa demand indicator in whichthermal ele-' ments, friction drives, and resetting mechanisms are eliminated, in which possibility of slippage 20 is overcome, and in which smooth and continu- .ous operation is obtained.

i Another object is to provide a demand indicator of the logarithmic-law type in which discrepancies from logarithmic response are jelimi- 25 nated.

Other and further objects and advantages will become apparent as the description proceeds.

In determining rates for the supp y of electrical energy by central stations, it is frequently desirable to determine a customers maximum 'demand or to obtain-a record of his demand at various times,"since the investment required by a central station is determined by the maximum load or demand for power rather than. by the average throughout the month'or year. In-

stantaneous peak loads in excess of the rated load of the apparatusof the central station may,

.7 however, be borneeby the apparatus if such peaks rdinfl y are of sumciently short duration; A

g demand indicators are used whichr nd'to the 'blocks of energy supplied within short intervals of time of the order of fifteen or thirty minutes rather than to the instantaneous power in kilowatts. Demand indicators are known of both 45 the .block interval and the logarithmic type.

meek interval demand indicators integrate the .load separately during each interval and are reset at 'the end of the interval, thus indicating the arlthmeti mean during the interval.

Logarithmic .demand indicators arein effect wattmeters with a considerable time lag 'an'dthey' integratewith respect to time'the difference between and the attained by the'indicator. v provide at any instant an indicatlon 'of 5 The principal object of my invention is to pro demand for a previous time period, the length of which depends upon the design of the indicator. In this respect, they have .the advantage over a block interval demand indicators of not missing peak loads which may happen to occur near'the 8 end of a time interval and thus be split between two intervals of the.' blocl: interval indicator. Furthermore, since the limiting factor in the loading of the equipment of the central station companyis the heating, which. follows a .logarithmic law, it. is of advantage to employ a demand indicator which follows the same law. Both thermally-operating and mechanicallyoperating logarithmic demand indicators are already known. The principle of,the thermal wattmeter is employed in the thermal type of lo'ga-' rithmic demand indicator described by Lincoln in .Transactions of the'American Institute of- Electrical Engineers 1'01 1915, Volume xmv, pages 2279 to 2318. Mechanically-operating demand indicatorsavoid discrepancies from a true logarithmic law occurring in thermal demand indicators owing to certain physical limitations of available material and also owing to the ifect of radiation in thermal indicators. Logarithmiclaw mechanical demand indicatorasuchas those disclosed .in Patent No. 1,33l,059 to Hall or in volume 53 of Electrical Engineering for January, 1934, pages 94 to 96, consist of a watt-hour meter I shaft rotating at a speed proportional to-instantaneous load, a constant-speed shaft.- a rotatable member, a variable velocity-ratio friction drive between the constant-speed shaft and the rotatable member, and means responsive to difference in speed between the watt-hour meter shaft and the rotatable member for adjusting the friction'adrive' to bring the speeds ofthe watt-meter shaft and the rotatable membu into conformity. In accordance with 'ny invention in its preferred form, I likewise provide a primary element or eifect responsive to the instantaneous value of a quantity to be measured, a secondary element or'en'ect, and means, for bringing the'\ secondary element or efl'ect into conformity with th'eflrstatarate proportionaltothediiference between them. However, I utilise mechanical connections providing a positive drive in, order to prevent slippage. In carrying out my invention in its preferred form, induction motor eleio'rmity. suitable characteristics, as speedortorquemay'iormthebasisoicomparison otthe actionotthetwo elements.

The ieatures of my invention which are be-. a lieved to be novel and patentable will be pointed out in the claims appended hereto. A better \mderstanding of my invention may-be obtained by referring to the following description taken inlimited to the measurement of quantities in electrical distribution circuits; Nor is its-use in electrlcal distribution circuits limited to the measurement oi real-power demand as it obviously includes also the measurement iii-apparentpower demand and reactive-component-ct-power demand g Beierringnowmoreindetailtothedrawing'in which like reference characters are utilised to load l2. :Ih'e apparatus includes; load-responsive primary torque-producing unit lland 'acting in opposition thereto; an adjustable strength secondary torque-producing'unit II with means tor continually adjusting the strength ot'the unit It to correspond to that of the load-responsive prise a mechanismsimilar to an induction watt! 'hour' meter mechanism having a schematically represented laminated ii'eld core ii and a rotatable disc ii cooperating with the held. The field core ii carries a potential winding "connected acrossthesouree [Landacurrentwinding ll connectedin series with the load l2.

To energize and control the adjustable torqueproducing unit there are provided an auxilin! source of current unit'll-may also'comprlse a mechanism of the induction'watt-hour meter type with a'laminated fleld core'll, represented schematicallmlnd with potential and current windings 2 and II, respectively. -However, for the sake of simplicity, I prefer to'mount ashading coil 22! on oneof-the polepieces oi! the'core 2i and energizethe unit either a current orpotential winding,'dependim uponthevoltageotthesouroe Ilandthet'ype ot circuit controller "employed, The unit It also includes aninduction disc cooperating with the and 2i -ifor;the sakeofcompactness but. ii. it is desiredto eliminate any possibility oi interaction I! and ii, separate discs mav beemployedwhichmaybemountedon acornwhich Fig, 1 represents a diilerential torque type adjustable comparison quantity and is notdesignate like parts throughput, in the arrangerment illustratedin Fig. l, the apparatus is shown connected toan electric system ll supplying a:

unit II. 'I'he'load-responsive unit it may compla I! and a circuit controller 20 through which the current from source I! is sunnliedto the windings oi themit ll. The

.tentin of the torque onlythroughoneoiitswindingsllwhichmaybe the W field core ii. In thearrangement illustrated inf disc I is common to field cores II um or'maybeotherwisemechanically Amy suitable arrangement may be employedv ior adiustinsthe torque of the secondary unit ll. Fbresample,theadjustmentmaybemadeby 5 warms thervoltage orcurrent in the winding 2:. B! W oi! illustration. I have shown the circuit controller 2. taking the form of a resistance potentiometer with a mo'vable contact II serving to vary-the voltage appliedto the winding 2! 6 according to-the position of the contact 25. The movable contact I is mechanically connected to the shaft 2| carryingthe rotatable disc It in such a manner that rotationoi the disc It moves the contact ii in the. required to equalize the torques Speed reduction gearing I is interposed between shaft 24 and themovable contact 2' in order tocause the torqueadjustment to take place gradually and to represent the Q,

mean value or the loadmeasuredbythe unit ll overaprecedingtimeinterval- 'lithesource llhasasubstantiallyconstant voltage orthearransementis such thatthe operation'ot the unit I4 .is indepe'ndcnt'oi' voltage fluetuations,'the position or the contact as wm g;

representtheloaddemand. Howevenit desired, acurrent device I'lmaybeconnected inserieswiththewindingfltoserveasanindi- 'cationoi the adjustment of the unit it and,

thereiorqof the load demand. The current-reso nspon'sive device TI may take the iorm,-ior ex-' ample, 01 an indicating or. a curve-drawing sin- IidnariredJtmaybeprovidedwithboth an indicating pointer 20 anda maximum pointer;

The principle of operation of the apparatus is 40 apparent fromtbe roregolns description or its ements. The torque. of the load-responsive I! will with variations in the momenotthepowerdrawn hy-theload-II,

the

the indication of the instrument} 21 will depend upon the setting o! the circuit controller 2., which tends to 10110 v variations in the torque-of the unit it, bututllyie final adjustment cannot take The rate at which the movable contact 15 is movedds coal to the difference in the tom, takes place less and les rapidly'as the ae- 'tiom'otthetwotomue-producingunitsapproach on and theoreticallyfan infinite-period req i for complete equallwhat is called the logo- 'quirediorthetorqueof the'seeondary unit to a predetermined fraction, such as nine: or the primary unit, when primary is sustained at a constant since the rate of adjustment of thesesis greatest when the deviation between its torque setting and the torque oi the primary. unit is greatest, load peaks 01f short duration'will havemoreeflectonthe apparatusthanloads 'fliem'aximllmpointerllisarrangedtobess' adjustable torque'unit II and ing units or motors for producing torques representing the momentary value and the periodic mean value, respectively, of a measured quantity and arranged to have the torque of one unit I brought into conformity with that of the other. However, it will be understood that my invention a the purpose'of explaining its principle and showis not limited to-this' precise construction but in-V .-the speeds rather than the torques are brought The secondary adjustable into conformity.

torque-producing unit II is provided with an independent rotatable disc ll in the arrangement Q 'of Fig. 2 and a differential "is provided for comparing the speeds of thediscs l8 and II. The

differential ll comprises sun gears}! and Il mechanically connected to the discs I! and SI, re-: spectively, andplanet gears" carried by a plane- 2 5 taryhouslng as.

The planetary housing 35 carries the movable contact 2,! of the resistance potentiometer lil and also carries a pointer 38 cooperating with a scale 1 31; It will be apparent that, if the adjustment 80 of the potentiometer II is such that the torqueproducing units l3 and I l rotate theplanet gears, 32 and l! at different speeds, the housing 35 will be rotated in one direction or another, causing the movable contact 2! tb slide along the potentiomeas ter an and bring the speeds of the units n and ll into conformity.

The discs lland 3|! need 4 not necessarily, rotate at the same speed when 1 the housing is stationary, since different gear ratios maybe employed between thediscs and o the corresponding sun gears of the din'erential ii. If the voltage of the source ills substan tiallyconstant, the speed of the disc I. will deducting winding, means for supplying an adpend on ',the position attained by the-movable contact and the demand may, therefore, 'be

45 read from the scale 31; "If the voltage of the source. is tends to vary, demand readings are preferably obtained'from the ammeter I].

A modified arrangement for causing the ad- I jus'table torque unit in to adjust its action in 60 conformity to the speed of the load-responsive unit is is illustrated in Fig. 3. In this arrange-' ment, no mechanical differential is employed but the"resistance potentiometer II .is arranged in annular form and is axially mounted upon a. 55 shaft II mechanicallyconnected through the reduction gearing Itto the shaft 24 of the load-reto suitable gearing to it shaft 4| carrying the be apparent that, until the shaft 4| has reached a speed corresponding to but not necessarily him, so connected to. said movable member as to disc 30 of the adjustable torque unit II. It will equaling the of the shaft ,relative rho- 65 tion-will take place betweenthe annular potentiometer II and the movable contact 25', 'bringing'aboutt a change in the speed of-the shaft llofthe'adiustable torque unit II. The logarithmic mean value of the load tobe measured may, thereing an output proportional to the to fore, be determined by means of a suitabl'y' calibi-ates instrument :1 as in the embodiments of my invention shown in Figs. 1 and 2.

I have herein shown and particularlydeseribed certaints ofimy inventiomand cer.

7 of operation embraced therein for ing its application, but it will be obvious to'those skilled in the art that many modifications and variations are possible'and I aim,"therefore, to

cover'all such modifications and variaions as I fall within the scope of my invention which is deflnedin the appended claims.

What I claim as new and desire tov secure b Letters Patent of the United States; is:

1. A demand indicator comprising in combination, an integrating electric motor, a. rotating shaft. driven thereby, a" second rotating shaft, 0.

motor driving said second shaft, means for supplying current to said motor, means responsive to the difference in speeds ,of said shafts; and is justable current thereto having a movable adjusting memberm'echanlcall'y so connected to said rotatable member as to be moved thereby in a 8 0 I direction required to balance the torques of said torque-producing mechanisms.

3. A demand indicator comprising in combination, a mechanism for producing a torque pro-.

portional to the momentary value of a quantity, :5

the demand for which is to be indicated, a countertorque-producing mechanism, said torqueproducing mechanisms having a common r0 table member, 'saidcountertorque-producing mechanism having an energizing current-con- 4f iustablecurrent thereto having a movable adlusting member, a reduction gearing mechanically connecting said movable. adjusting member and said rotatable member and arranged totmove said adjusting member in a direction re-'" quired to balance the torques in, said torqueproducing mechanisms: 0' 4.-A demand indicaton; comprising in combination, a pair of, torque-producing mechanisms acting in opposition, one of said mechanisms hav 'ing a torque proportional to the momentary value of the quantity the demand for which is to be indicated and theother or saidmechanisms having an adjustable torque, a member acted upon jointly by said torque-producingmechanisms and movable in response to unbalance in their actionsl' and movable means for adjusting the torque of saidlatter torque-producing mechato be moved-thereby in a direction required to balance the action of said torque-producing 5. A demand indicator comprising in combina- I tion a pair of torque-producing mechanisms acting in conjunction, one 0L said mechanisms havmomentary value of a quantity, the demand for whichgis to ,be indicated, and theother of such mechanisms having an adjustable output, an adjustable de- I0v vice acted upon joint y by said-torque-producing mechanisms arranged to have its adjustment va ried when said m not thereon unequal-- ly,said,devic'e being so connected to said adjust-- able torque-producing astoyary; 15 m 4E v 7 the output thereof in the toequalize the action of said torque-producing mechanisms.

8. A demand indicator comprising tion, a pair of torque-producing mechanisms act- 1" ing in conjunction, one of said mechanisms having an output proportional to the momentary value of a quantity, the demand for whichis to be conducting winding, a circuit controller acted -tion, a pair of motors acting in 'of'said m'otors having a speed p indicated, and the other of said torque-producing mechanisms having an energizing currentupon jointly by said torque producing mechaa source of current connected to the enerwinding of said latter torque-producing 'mechanism and controlled-bysaid circuit controller, said circuit controller being arranged to be so acted upon by the joint action of said vtorque-producing mechanisms as to vary the current in said energizing winding in the'jdirection required to equalize the action of said torque- *rent to said winding acted upon jointly by said torque-producing mechanisms. the arrangement being such that the current magnitude is varied in response to unequal action of said torque-pro ducing mechanisms in a direction required to equalize said action, and a current-responsive device connected in series with said winding and said adjustable current source. V

8. A demand indicator comprising incombinaunction', one

momentary value of the quantity the demand for which is to'be indicated, the other of said-motors having an adjustable speed. shafts driven by said motors,- means responsive to the difference in 3. speeds of saidshafts, and means controlled by for varying the speed of the adjustable speed motor in such a direction as to equalize the speeds of said shafts. Y

9. A demand meter comprising in combination.

a motor rotating at a speed the rtional to-the liatent idated November 12, 1935.- asslgnee, ompiz'hyfj}. Hersh sigma thisdisclainier welaimsi momentary value of the quantity the demand for which is' to be indicated, an adjustable speed motor, movable means for controlling the speed of said adjustable speed motor, a. differential mechanism having rotatable elements mechani 5 cally connected to said motors. and an element movable in response to the diflerence in speeds of said rotating elements, said movable element being so connected to the speed controller 01' said adjustable speed motor as to equalize the speeds of the rotating elements of said diiierential mechanism. T

10. A demand'indicator comprising in combination, a motor having a speed proportionalto the momentary value. of the quantity the de- 16,

mand for which is to be indicated, an adjustable speedlmotor, {source of current energizing said adjustable speed motor, and a'circuit controller interposed between said current source and said motor to vary the speed thereof,-said circuit con- 26 'troller having a pair'of relatively movable elements to vary theadjustment thereof, one'of'said elements being mechanically connected to one of said motors and the other being connected to the other of said motors, the arrangement being such that differences between absolute 89 1 of the elements of said circuit controller vary the adjustment thereof to bring the speed of the adiustable speed motor into conformity with that of the'other motor. l

11. A demand indicator comprising in com-- bination, a'unit ac'ting'with a force proportional to-the momentary value of the quantity the demand for which is to be indicated, a second unit acting with a force proportional to the'logarith- '35 mic mean during the preceding time of the .force of said first unit; and means producing an indicationvarying .unit varies. a 1 I 12. A device for indicating the ligarithmic 40 as the force of said second means for the preceding time. of the action of a movable member comprising in combination with said movable member, a second movable member,

means forbringing the action of said second member into conformity with that of the flrst member at a rate continuously p p rtional to the. diil'erence in their action, and means responsive tothe action of saidsecondmember.

1 v V A lin Karlshorst, Disclaimerined mil- 31 ,1937, by the 4E v 7 the output thereof in the toequalize the action of said inrque-producing mechanisms.

8. A demand indicator comprising tion, a pair of torque-producing m acting in conjunction, one of said mec having an output proportional to the momentary value of a quantity, the demand for whichis to be conducting winding, a circuit controller acted tion, a pair of motors acting in 'of'said m'otors having a speed p indicated, and the other of said torque-producing mechanisms having an energizing currentupon jointly by said torque producing mechaa source of current connected to the enerwinding of said latter torque-producing 'mechanism and controlled-bysaid circuit controller, said circuit controller being arranged to be so acted upon by the joint action of said vMarque-producing mechanisms as to vary the current in said energizing winding in the'jdirection required to equalize the action of said torque- *rent to said winding acted upon jointly by said torque-producing mechanisms. the arrangement being such that the current magnitude is varied in response to unequal action of said torque-pro ducing mechanisms in a direction required to equalize said action, and a current-responsive device connected in series with said winding and said adjustable current source. V

8. A demand indicator comprising incombinaunction', one

momentary value of the quantity the demand for which is to'be indicated, the other of said-motors having an adjustable speed. shafts driven by said motors,- means responsive to the difference in 3. speeds of saidshafts, and means controlled by for varying the speed of the adjustable speed motor in such a direction as to equalize the speeds of said shafts. Y

9. A demand meter comprising in combination.

a motor rotating at a speed the rtional to-the liatent idated November 12, 1935.- asslgnee, ompiz'hyfj}. Hersh enters thisdisclainier to c'laim's i a GWWAWW, 19 J i momentary value of the quantity the demand for which is' to be indicated, an adjustable speed motor, movable means for controlling the speed of said adjustable speed motor, a. differential mechanism having rotatable elements mechani sally connected to said motors. and an element movable in response to the diflerence in speeds of said rotating elements, said movable element being so connected to the speed controller of said adjustable speed motor as to equalize the speeds of the rotating elements of said diiierential mechanism. T

10. A demand'indicator comprising in combination, a. motor having a speed proportionalto the momentary value. of the quantity the de- 16,

mand for whichis to be indicated, an adjustable speedlmotor, {source of current energizing said adjustable speed motor, and a'circuit controller interposed between said current source and said motor to vary the speed thereof,-said circuit con- 26 troller having a pair'of relatively movable elements to vary theadjustment thereof, one'of'said elements being mechanically connected to one of said motors and the other being connected to the other of said motors, the ent being such that differences between absolute 89 1 of the elements of said circuit controller vary the adjustment thereof to bring the speed of the adiustable speed motor into conformity with that of the'other motor.

11. A demand indicator comprising in com-- bination, a'unit acting'with a force proportional to-the momentary value of the quantity the demand for which is to be indicated, a second unit acting with a force proportional to the'logarith- '35 mic mean during the preceding time of the .force of said first unit, and means producing an indicationvarying .unit varies. a 1 I 12. A device for indicating the ligarithmic 40 as the force of said second means for the preceding time. oi the action of a movable member comprising in combination with said movable member, a second movable member,

means forbringing the action of said second member into conformity with that of the flrst member at a rate continuously p p rtional to the. diil'erence in their action, and means responsive tothe action of saidsecondmember.

1 v V a lin Karlshorst, Disclaimerined March 3iti937, by the 

